Molecular beam reaction of the van der Waals clusters (CH3I)n with alkalis

The reactions of K and Rb with van der Waals clusters (n−mers) of methyl iodide, (CH3I)n, have been observed via the crossed molecular beam technique. Under strong expansion conditions, seeded nozzle beams of CH3I contain significant fractions of n−mers: all n ? 6 have been observed directly in the beam by electron bombardment ionization and mass filter detection of the parent ions. Upon heating of the nozzle, the weakly bound ’’polymers’’ revert readily to monomer. Crossing the cluster beam with an alkali beam and using a surface ionization scattering detector of high work function, a sharp peak appears superimposed on the angular distribution of KI (RbI) (that due to the alkali reaction with monomer), which disappears as the CH3I polymers are converted back to monomeric form. From the over−all body of evidence it is inferred that this peak is due to a fairly high molecular weight product (or semistable complex) formed by the reaction of an alkali atom with a methyl iodide cluster molecule (CH3I)n of n? 3.